The present invention relates generally to fluid devices used to convert a steady fluid flow to an intermittent pulsating flow, and more particularly, to a fluid pulsating generator which utilizes intermittent pulsating fluid flow to generate electricity. Some applications of the present invention include pulsating irrigation devices such as sprinklers, misters and drippers used for irrigation purposes. While the present invention is particularly suitable for use with irrigation systems, the fluid pulsation generator of the present invention can be utilized many other fluid-driven devices which produce a pulsating fluid flow that can harvested into electrical energy.
The use of irrigation devices, or other fluid devices or appliances, to generate electricity is well known. Such devices often include an impeller positioned within the device, such as within a hose, pipe or other housing, which is rotated as the fluid, such as water, flows past the impeller. The impeller is often coupled to the rotor portion of a generator such that the rotor of the generator turns as the fluid flows past and turns the impeller. However, often, the use of an impeller-driven generator expends some of the force of the fluid, thereby reducing fluid pressure down stream from the impeller. In the case of an irrigation sprinkler system, such reduction in fluid pressure can reduce the fluid distribution area of the sprinkler.
Other devices known in the art to generate and harvest electrical energy utilizes the physical phenomenon known as piezoelectricity. Certain materials, such as particular crystals, have physical properties which allow the material to generate a voltage (electricity) in response to an applied mechanical stress or “deformation” to the material. This ability of the material to generate such a voltage is referred to piezoelectricity or the “piezoelectric effect.” Generally, the word piezo is derived from the Greek word piezein, which means to squeeze or press. This piezoelectric effect is also reversible in that piezoelectric crystals, when subjected to an externally applied voltage, can change shape by a small amount. As such, piezoelectric elements find useful applications in many products such as in the production and detection of sound, the generation of low to high voltages, electronic frequency generation, microbalance and ultra fine focusing of optical assemblies, to name just a few applications.
Piezoelectric elements have been utilized in a number of different devices for developing an energy harvesting system that recovers what would otherwise be wasted mechanical energy. Such piezoelectric elements can convert mechanical energy from a number of sources into useful electrical energy which can be stored and/or used to charge other electrical devices. Electric circuitry has been developed which can be connected to the piezoelectric element for developing and storing the generated output voltage from the piezoelectric element.
What has been needed is a fluid pulsating generator which can use otherwise wasted mechanical energy developed by a fluid pulsating device, such as a sprinkler, to generate and store electrical energy. Such a generator should not adversely affect the performance of fluid pulsating device and should be easily incorporated into such a device. The present invention satisfies these and other needs.